Glosbe - Huge collaborative massively multilingual dictionary.
Wordnik - the biggest online English dictionary, by number of words
VerbAce - VerbAce-Pro is an easy-to-use Desktop Translation Software. Translate in a mouse click
Visuwords - The fun and free way to look up definitions. THE graphical dictionary and visual thesaurus.
Advanced English Dictionary - Advanced English Dictionary is better than other dictionaries, not just because it contains far...
NextDict Dictionary - NextDict is a multi-language dictionary and a collection of the most complete English references...